Abstract
The electronic structures of R B~6~, R B~12~ and R B~2~C~2~ borides are studied ab initio by using the full‐potential linear muffin‐tin orbital method. This study includes the promising materials for spin electronics with reported high temperature ferromagnetism, namely, doped divalent hexaborides CaB~6~, SrB~6~, BaB~6~, and the CaB~2~C~2~ compound, as well as Kondo semiconductors, SmB~6~ and YbB~12~. For CaB~6~ and SrB~6~ a semiconducting band structure has been obtained, whereas a semimetallic ground state is revealed for CaB~2~C~2~ and doped hexaborides. For YB~6~, LaB~6~, CaB~2~C~2~ and the semimetallic Ba~1–x~ La~x~ B~6~ alloys we have performed spin‐polarized band structure calculations in an external field to evaluate the induced spin and orbital magnetic moments. These calculations indicate a feasibility of the field‐induced weak ferromagnetic phase in CaB~2~C~2~ and the La doped hexaborides. The LSDA and GGA calculations for different spin configurations of YbB~12~ point to a possibility of antiferromagnetic coupling between Yb^3+^ ions. For SmB~6~ and YbB~12~ our LSDA, GGA, and LSDA+U calculations have not revealed the hybridization gap for configurations with trivalent Sm^3+^ and Yb^3+^. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)